Chapter 1.10, Problem 8LTS

Interpretation Introduction

Interpretation: The geometry of a hydronium ion has to be predicted

Concept Introduction:

According to VSEPR (Valence Shell Electron Pair Repulsion) theory, each molecule gets a unique structure. That structure is explained by considering steric number of that molecule.

The steric number is the combination of both number of $\sigma$-bonds and number of lone pairs involved in a particular molecule.

$\sigma$-bonds are formed by the mutual sharing of electrons between the two atoms. As a result, bond between two atoms is formed.  This type of bond is called covalent bond.  In this process, bonding electron pairs are involved.

Non-bonding electrons are not involved in the bond formation. They are called lone pairs.

The geometry of the central atom will be determined by counting the steric number followed by the hybridization state of that central atom and finally electronic arrangement of atoms in space.

If the steric number is 4, the central atom has sp³ hybridized and the electronic arrangement of atoms in space (i.e. geometry) will be tetrahedral.

If the steric number is 3, the central atom has sp² hybridized and the electronic arrangement of atoms in space (i.e. geometry) will be trigonal planar.

If the steric number is 2, the central atom has sp hybridized and the electronic arrangement of atoms in space (i.e. geometry) will be linear.

Steric number is calculated by using following formula,

$\text{Steric number}\text{=}\text{number}\text{of}\text{σ-bonds}\text{+}\text{number of lone pairs}$